Comments on: HOWTO: Use STM32 SPI half duplex mode

By: Pierre

Pierre — Tue, 07 Jun 2016 15:23:24 +0000

This is not what half duplex is. SPI is not a time-multiplexed protocol, it is a one byte in / one byte out protocol. Please read about full duplex and half duplex modes (for SPI) and correct your article. Half duplex with SPI only means you only have MOSI or MISO.

By: fikir

fikir — Tue, 12 May 2015 01:53:41 +0000

In reply to Baoshi. Thank you for your reply. I'm going to add chip select signal to my fpga and the reason why I want to use the spi bus is because I'm planning to add few other sensors.

By: Baoshi

Baoshi — Tue, 12 May 2015 01:43:10 +0000

In reply to fikir. Hi, I think your case it is not standard SPI. It is more likely to be synchronized serial mode. I'm not too sure but if you're using STM32 you should be able to config USART in synchronized mode and use it directly.

By: fikir

fikir — Mon, 11 May 2015 00:54:58 +0000

Hi, I have a question. Let say my slave device has no chip select pin. My slave is an fpga and I didn’t make chip select pin. Basically, the fpga will produce serial data out as long as the spi_clk is there and I don’t need the master to send any data. So, in the above code, during the sending 1 byte by master, the spi_clk is produced or not?

In my case, I would like the spi_clk to only be there when the master is ready to receive data. So, if the master produce 8 clock cycles, the master will receive 8 bit of data. If the clock stop, no data will be coming from the slave. Once the fpga(slave) has sent all the data, the fpga will sent a read_complete signal and all the communication will stop.

Therefore it is important for the master to only send the clock during receiving mode only. Is this what is meant by `transmitting mode to stop the clock’ in the above code?

By: replay1

replay1 — Fri, 17 Oct 2014 10:56:03 +0000

good one! Wish you would make similar tutorial about I2C bus too.

Keep up the good work!